Plant Unit Notes 4 of 5 Name: Hour: Chapter 29: Plant Structure & Function (of roots, stems, & leaves) Pages 582-607 Targets: 18-24

Review of Main Plant Cell Parts: Large fluid-filled vacuole - provide turgor pressure for support & store water for dry spells Plastid: pigment containing organelles Thick cell wall - made of cellulose for support, that surrounds the cell membrane

Plants are made up of 3 types of cells Parenchyma Cells Thin flexible cell walls, cube-shaped Large central vacuole Function: photosynthesis, storage, & healing Ex: flexible green stems, & fleshy fruit (Apples) Collenchyma Cells Thicker cells walls; irregular shape Function: support for growing plant parts Ex: areas still lengthening (Celery stalks) Sclerenchyma Cells Thickest/rigid cell wall Function: strength & support for non growing plant parts; usually dies at maturity Ex: a frame to support the plant (shell on nut)

3 Types of Plant Tissue Systems Location Function in Roots Function in Stems Function in Leaves Dermal Tissue (epidermis) outer most layer -cuticle -stomata absorption; protection gas exchange; protection Ground Tissue b/w dermal & vascular support; storage Photosynthesis Vascular Tissue Tubes throughout plant transport; support

Vascular Plant Tissue: Xylem: - Dead at maturity - Transports water - 2 Cell Types - Tracheid: tapered ends; pits to allow water to pass through - Vessel Elements: larger holes at top & bottom Phloem: - living at maturity -Transports organic material - 2 Cell Types - Sieve Tube: filters - Companion Cell: assists in transport along sieve tube http://www.sirinet.net/~jgjohnso/plants.html http://www.sirinet.net/~jgjohnso/plants.html

Plant Growth: Meristems: where plant growth originates (cells continually divide) Apical Meristems: increase length @ tips Location: Tips of stem & root Intercalary Meristems: increase length b/w nodes Location: b/w tip and base of stem & leaves *why grass can regrow after being mowed Lateral Meristems: increase diameter Location: outsides of stems & roots 2 Types: Vascular cambium (b/w xylem & phloem) Cork cambium (outside phloem = makes cork) Primary Growth: growth in length (apical & intercalary) Secondary Growth: growth in width (lateral)

Concept Check What is the function of a plant vacuole? - provide turgor pressure for support & store water for dry spells Name the 3 types of plant tissues - dermal, vascular, ground (a 4th could be meristematic) Name the 3 types of cells found in plants - Parenchyma Collenchyma Sclerenchyma

Plant Organs: Roots (typically grow underground) Function: anchor in place, transport water & mineral nutrients, and storage of water & organic compounds Types of roots: Taproot: 1st root is the largest; generally not deep rooted Ex: Carrot, radish Fibrous Root System: numerous roots develop & branch Ex: Grass Adventitious: grow roots from above ground parts (stems & leaves); prop roots of corn & aerial roots of vines

Root Structures Root cap : protects apical meristem, produces “oil” Root hairs: increase surface area for water absorption (mycorrhizal fungi) Cortex: ground tissue just inside of epidermis Endodermis: ground tissue found inside the cortex; has a waterproof substance to control water & mineral movement Vascular Tissue: innermost core of roots. Dicot: “X” shaped xylem with pockets of phloem Monocot: pith in the middle with alternating xylem & phloem in a ring Pericycle: outer layer of vascular tissue; produces lateral roots

Plant Organs: Stems (typically above ground, upright & woody or non-woody) Function: support leaves, transport material, provide storage Special Types of stems: (due to adaptations to the environment) Stolons: grow along soil to produce new plants Tubers: underground; modified for storing energy as starch Fleshy stems: store water and carry out photosynthesis

Stem Structures Node: where a leaf is attached to a stem Internodes: space between the nodes Bud: where a new shoot can grow (stem or leaf) Bud scales: cover buds; leave scars after opening Primary Growth Pith: forms in center of stem in dicots; separates from cortex Vascular Tissue: Monocots: xylem/phloem in scattered bundles Dicots: xylem in/phloem out; form a ring in the cortex Look at extra picture handouts!

Stem Structures - Continued Secondary Growth: stems increase in thickness due to division of vascular cambium cells (b/w xylem & phloem) Wood: secondary xylem Heartwood: darker wood; older, does not transport water Sapwood: lighter wood; still transports water Bark: phloem near outside of stem; for protection (made of cork, cork cambium, and phloem) Springwood: wood cells wide & thin walled; more water present Summerwood: wood cells small & thick walled; lack of water Annual Ring: created by difference in appearance (not seen in tropical plants, why?)

Stem Function: transport, storage, support leaves Transport of sugar through phloem (translocation) From source to sink by Pressure Flow Hypothesis Source: where sugar is made or stored Sink: where sugar will be stored or used *sugar mainly made in leaves - moved to rest of plant Transport water & dissolved minerals through xylem (transpiration) Water pulled up by Cohesion-Tension Theory Water molecules stick together; cohesion Water molecules stick to xylem; adhesion Water evaporates through stomata & pulls others along Storing water and nutrients Large amount of parenchyma cells to store: Water; cactus / Sucrose; sugar cane / Starch; potatoes

Plant Organs: Leaves (typically thin & flat) Function: Capture sunlight for photosynthesis Types of leaves: Tendrils: used to support & climb Spines: protection; non-photosynthetic Food traps: plants with poor soil nutrients Structure: Blade: broad flat portion of leaf Petiole: stalk-like attachment to stem Simple leaf: single blade Compound leaf: blade is divided into leaflets Can be doubly compound; leaflets divided

Leaf Structures Epidermis: Outside layer of cells Cuticle: waxy covering; prevent water loss Hairs: protect against insects & sun Stomata: tiny air pores, areas for gas exchange; number & location vary on plants Guard cells: regulate the size of the stomata Mesophyll: Ground tissue; chloroplast-rich Palisade: under upper-epidermis; tightly packed Spongy: under palisade layer; loosely packed, air spaces Veins: bundles of vascular tissue (parallel vs. branched)

Concept Check What is the function of the root cap? - protects apical meristem, produces “oil” What are the main differences b/w xylem & phloem? - xylem: dead at maturity; transports water; specialized cells: tracheid/vessel elements - phloem: alive at maturity; transports food; specialized cells: companion/sieve tube What difference b/w the stomata & the guard cells? stomata = space; gas (O2/CO2) passes through guard cells = cells; swell/shrink to control size of space